:root {
  --bg: #f4f6f8;
  --card: #ffffff;
  --text: #14202b;
  --muted: #5a6b7a;
  --accent: #0d8f5b;
  --accent-soft: #e6f7ef;
  --border: #d5dde5;
  --warn: #0d5c3d;
  --shadow: 0 8px 24px rgba(20, 32, 43, 0.06);
  font-family: "Segoe UI", system-ui, sans-serif;
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text); line-height: 1.55; }
a { color: var(--accent); }
.top {
  display: flex; justify-content: space-between; align-items: center;
  padding: 0.85rem 1.25rem; background: #fff; border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 10;
}
.logo { font-weight: 800; text-decoration: none; color: var(--text); font-size: 1.1rem; }
nav a { text-decoration: none; color: var(--muted); font-weight: 600; }
.wrap {
  max-width: 640px; margin: 0 auto; padding: 1.25rem 1rem 3rem;
  display: flex; flex-direction: column; gap: 0.75rem;
}
.wrap > h1 { order: -3; font-size: clamp(1.5rem, 4vw, 1.9rem); margin: 0.4rem 0 0; line-height: 1.2; }
.wrap > .lede { order: -2; color: var(--muted); margin: 0 0 0.25rem; font-size: 1.05rem; }
.wrap > .tool { order: -1; }
.formula, .example, .tool, .faq, .related, .embed, .money, .meta, .meta-details {
  background: var(--card); border: 1px solid var(--border); border-radius: 14px;
  padding: 1.1rem 1.15rem; box-shadow: var(--shadow);
}
.formula, .example { font-size: 0.95rem; color: var(--muted); }
.formula h2, .example h2, .money h2 { font-size: 0.85rem; text-transform: uppercase; letter-spacing: 0.04em; color: var(--muted); margin: 0 0 0.5rem; }
label { display: block; margin: 0.65rem 0; font-weight: 600; font-size: 0.95rem; }
input, select, textarea {
  width: 100%; margin-top: 0.35rem; min-height: 48px; padding: 0.7rem 0.8rem;
  border-radius: 10px; border: 1px solid var(--border); background: #fff; color: var(--text);
  font-size: 1.05rem;
}
input:focus, select:focus { outline: 2px solid var(--accent); border-color: var(--accent); }
.btn {
  display: inline-block; margin-top: 0.85rem; padding: 0.85rem 1.2rem; min-height: 48px;
  background: var(--accent); color: #fff; border: 0; border-radius: 10px;
  font-weight: 800; font-size: 1.05rem; cursor: pointer; text-decoration: none; text-align: center;
}
.btn-lg { width: 100%; }
.btn:active { transform: scale(0.98); }
.result {
  display: block; margin-top: 1rem; padding: 1rem; border-radius: 10px;
  background: var(--accent-soft); color: var(--warn); white-space: pre-wrap;
  font-size: 1.15rem; font-weight: 700; line-height: 1.4;
}
.lede-tight { margin: 0 0 0.75rem; color: var(--muted); }
.muted { color: var(--muted); font-size: 0.9rem; }
.cols { columns: 2; gap: 1rem; margin: 0; padding-left: 1.1rem; }
.foot { padding: 1.5rem; color: var(--muted); font-size: 0.85rem; text-align: center; }
details.meta-details summary { cursor: pointer; font-weight: 700; }
.cluster { margin: 1.25rem 0; }
.cluster h2 { font-size: 1.1rem; margin: 0 0 0.5rem; }
.cluster ul { list-style: none; padding: 0; margin: 0; display: grid; gap: 0.5rem; }
.cluster a {
  display: block; padding: 0.85rem 1rem; background: #fff; border: 1px solid var(--border);
  border-radius: 12px; text-decoration: none; color: var(--text); font-weight: 650;
  box-shadow: var(--shadow);
}
.cluster a:active { background: var(--accent-soft); }
.pay-qr { max-width: 240px; width: 100%; border-radius: 12px; border: 1px solid var(--border); }
@media (max-width: 560px) { .cols { columns: 1; } }